feat(cli): run an analysis without questions from flags (#1127, #1133)

- --ticker, --date and --analysts answer their steps, checked as the prompts check them; --save/--no-save and --show/--no-show answer the questions after the run
- with no terminal, the run stops before it starts and names every flag or TRADINGAGENTS_* variable still needed; a missing API key and an announcement no longer wait for input
- README shows an unattended run

tests/conftest.py

@@ -45,6 +45,15 @@ def _no_network(request, monkeypatch):
     monkeypatch.setattr(socket.socket, "connect_ex", refuse)
 
 
+@pytest.fixture(autouse=True)
+def _at_a_terminal(monkeypatch):
+    """Tests of the interactive steps run as if at a terminal; pytest's stdin is
+    not one. A test of an unattended run sets isatty to False itself."""
+    import sys
+
+    monkeypatch.setattr(sys.stdin, "isatty", lambda: True)
+
+
 @pytest.fixture(autouse=True)
 def _own_cli_prefs(tmp_path, monkeypatch):
     """The CLI keeps the last run's selections in the user's home; tests keep theirs apart."""